Cord Reel Including A Conductive Polymeric Sheath With A Conductive EMI Drain

ABSTRACT

A cord reel cable including a polymeric sheath with a conductive EMI drain and a method of manufacture therefor. The cord reel includes a cable comprising power and data conductors, as wells as a single drain wire which is grounded to a cord reel housing or spool or the like. The drain wire contacts an outer ETFE layer surrounding the cable in order to provide EMI shielding to the cable.

PRIORITY OF INVENTION

This Application is a Continuation of Ser. No. 14/618,545 filed on Feb.10, 2015, which claims priority to Provisional Application No.62/090,163, filed Dec. 10, 2014.

FIELD OF INVENTION

The present invention relates to a system for the retractable deliveryof an electrical connection via cord reel. More specifically, thepresent invention relates to a cord reel having multiple conductorscomprising an outer jacket of a conductive polymeric material and drainor drain wire amongst the conductors which contacts the outer jacket inorder to reduce or eliminate electromagnetic interference into thecable.

BACKGROUND OF THE INVENTION

Retractable reels have been used in various applications to retractablystore various types of cables. For example, one successful cord reelassembly has been developed that comprises a spool on which theextendable portion of cord is held, an expansion chamber in which afixed length of cable is spirally wound. The two cable portions areconnected, typically in or adjacent the hub of the spool. As the spoolrotates the spirally wound, fixed cable expands and contracts within theexpansion chamber. An example of reels of this type is disclosed in U.S.Pat. No. 5,094,396 to Burke, the disclosures of which are herebyincorporated by reference.

In order to provide a usable product for a variety of operatingenvironments for such cord reels, it is necessary to provide a mechanismto enable the prevention of interference (e.g., EMI/RFI). However, sincethe kinds of cords reels involved often require repeated winding andunwinding, whatever EMI protection is used needs to be flexible anddurable.

DESCRIPTION OF THE PRIOR ART

Those of skill in the art understand that conductive shields (e.g.,copper layers) may be used to great success in preventing EMI and crosstalk in a cable. For instance, U.S. Pat. No. 7,692,099 (Burke), teaches(among other things) the use of tinned copper shielding comprising 38AWGtinned copper with an inner shield minimum of 90% EMI coverage and anouter shield minimum of 85% coverage. Likewise, such teachings includethe use of a copper shield for individual conductors to eliminatecrosstalk between such individual conductors in the cable. Such priorart approaches further teach the use of additional layers outside thebundle of conductors to improve durability, such as a further Teflonlayer and a braid jacket covering. Such approaches, while useful in avariety of applications, have their limitations. For instance, suchshields will have a tendency to “whisker” or fray over time.Additionally, the use of multiple layers may limit the flexibility ofthe resulting cable, depending upon the desired application.

Alternatively, certain prior art approaches teach the availability ofencapsulation techniques for wire assemblies. However, many materialsfor encapsulation do not have the desire strength and/or flexibility tobe employed in a cord reel cable, nor do many materials have thenecessary flame, smoke and toxicity resistance required of many cordreel assembly applications. In addition, such approaches do not enablethe production of cable assemblies with multiple wire componentsconnected to one another, such as the “flat-round” cable assemblyreferenced above. For instance, in order to enable the manufacture of a“flat-round” cable, it is necessary to have an exposed cable end at thepoint of the flat-round junction. Thus, the use of encapsulate wire,without more, would require removing at least a portion of theencapsulation which would unduly degrade or eliminate any shieldingprovided by the encapsulation.

In sum, none of these prior art approaches peimit a cord reel_assemblyto provide a thinner or single layer covering for a multiconductor cablewith durability and EMI/crosstalk resistance.

What is needed is thin, durable and EMI/crosstalk resistant solution forthe manufacture of a cord reel assembly.

Definition of Terms

The following terms are used in the claims of the patent as filed andare intended to have their broadest plain and ordinary meaningconsistent with the requirements of the law.

“ETFE” is a polymer which is also known aspoly(ethene-co-tetrafluoroethene).

A “drain wire” is a single conductor which connects the ETFE to ground.

“Tinsel” is an electrical wire for application when high mechanicalflexibility is required.

Where alternative meanings are possible, the broadest meaning isintended. All words used in the claims set forth below are intended tobe used in the normal, customary usage of grammar and the Englishlanguage.

OBJECTS AND SUMMARY OF THE INVENTION

The apparatus and method of the present invention generally includes acable comprising a bundle of conductors including at least one powerconductor, at least one data conductor, and a single drain wire which isgrounded to a cord reel housing or spool or the like. The drain wirecontacts an outer conductive polymeric layer, such as ETFE in order toprovide EMI shielding to the cable. The ETFE is vacuum sealed around thebundle of conductors and does not extend to at least one end of thebundle of conductors so as to facilitate the connection of the cable toanother wire or cable in the assembly (e.g., by soldering). The crosssection of the cable further includes a core, with the bundle ofconductors being spaced around the core such that the drain wire issubstantially opposite the power conductor so as to minimize crosstalk.Further, the conductors other than the drain wire may be coated with aTeflon or similar coating, and the conductors are twisted around oneanother along the length of the cable so as to provide a helicalconfiguration to better resist EMI and crosstalk.

The immediate application of a present invention will be seen inflat-round cable assembly, though those of skill will see that thepresent invention could be applied to other cable assemblies where thecomplete encapsulation of the cable may not be practical.

Thus can be seen that one object of the present invention is to providea flexible, thin and durable EMI shield for a cable in a cord reelassembly.

A further object of the present invention is to provide an EMI shieldmechanism for a non-encapsulated cable in a cord reel assembly.

Still another object of the present invention is to provide a cord reelassembly with a drain for transferring external EMI away from dataconductors in the cable.

Yet another object of the present invention is to provide a cord reelassembly having superior EMI and crosstalk resistance.

Still another object of the present invention is to provide a cord reelassembly which reduces or eliminates whiskering or fraying in a cablewhile still providing acceptable flame, smoke and toxicity resistance.

It should be noted that not every embodiment of the claimed inventionwill accomplish each of the objects of the invention set forth above. Inaddition, further objects of the invention will become apparent based onthe summary of the invention, the detailed description of preferredembodiments, and as illustrated in the accompanying drawings. Suchobjects, features, and advantages of the present invention will becomemore apparent in light of the following detailed description of a bestmode embodiment thereof, and as illustrated in the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross section of a cable in accord with a preferredembodiment of the present invention.

FIG. 2 shows an exploded view of a cord reel assembly in accord with apreferred embodiment of the present invention.

FIG. 3 shows a partially exposed side view of a spool and cable inaccord with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Set forth below is a description of what is currently believed to be thepreferred embodiment or best examples of the invention claimed. Futureand present alternatives and modifications to this preferred embodimentare contemplated. Any alternatives or modifications which makeinsubstantial changes in function, in purpose, in structure or in resultare intended to be covered by the claims in this patent.

FIG. 1 shows a cable 10 having a cross sectional profile in accord witha first preferred embodiment of the present invention. The cable 10comprises a series of conductors 12, including at least one powerconductor 14 and at least one data wire 16. These conductors arepreferably of a thickness or wire gage of 28AWG, and are made of a 19/40stranded 135 alloy for this preferred embodiment. In addition, all ofthe conductors 12 of this embodiment preferably include an insulationlayer 18 made of 0.006″ of FEP or Teflon, except for the single drainwire 20. The drain wire 20 connects at one end to ground, such as a cordreel housing or spool (not shown).

Surrounding the bundle of conductors 12 is an outer layer 30 made up ofa conductive polymer such as PVC or ETFE to provide a flexible yetstrong cover for the conductors 12 while having desirable flameresistance, smoke resistance and non-toxicity characteristics. Theconductive polymer, however, does not fully encapsulate the cable, suchthat at least one end of the wire is exposed so as to enable the cableto connect to another cord (e.g., a flat wire) in a cord reel housing110 (as detailed in FIG. 2), as well as to enable the connection of thedrain wire to ground via a cord reel housing or spool (also not shown).One of the advantages of using such a drain wire 20 is that because theouter layer 30 is typically an extruded polymer, such a material makesit hard to crimp the outer layer 30 to a draining source such as achassis, housing or spool. Such combination of a conductive polymericouter layer 30 and drain wire(s) 20 thus reduce or eliminate radiatedemissions that enter the outer layer 30 from the conductors 12 inside ofthe shield and emissions that might come from the outside of the outerlayer 30. These emissions must be drained to a source such as thechassis. Thus, the drain wire(s) is used to absorb the emissions, andthe drain wire(s) are easily crimped to allow the radiated emissions todissipate. Of course, those of skill in the art will understand thatmore than more drain wire can be used with the present invention, andthat a given drain wire may be outside of the ETFE or similar outerjacket, so long as the drain wire is in contact with the surface of theouter jacket.

Preferably, the conductors 12 are twisted around a cotton core 40 orsimilar structure to maintain a circular cross section configurationalong the length of the cable, e.g., so as to make one 360 degreerotation around the core along a 1″ length of the cable. Such aconfiguration provides contact around the interior circumference betweenthe outer layer 30 and the drain wire 20 so that any EMI that permeatesthe outer layer 30 can be drained away to ground. In addition, in itsmost preferred embodiment, the drain wire is spaced apart from the powerconductor 14 so as to be substantially across from the cotton core 40.This spacing provides superior resistance to any crosstalk adverselyimpacting the performance of the cable 10.

The conductive polymeric layer can be terminated to a connector withoutthe at least one drain wire by having the connector strain reliefgrip/crimp onto the jacket and connect to the connector housing for ashield connection.

Those of skill having the teaching of the present invention willrealize, however, that alternative embodiments can employ a drainfeature which does not require a “drain wire,” per se, but does includea drain for draining EMI. For instance, the conductive polymeric layer30 can also be ter ninated to the housing of a connector if a mold isformed with a conductive polymeric material that contacts the connectorhousing for a shield connection. A further alternative for providingsuch a drain could be enabled by terminating the conductive polymericlayer 30 to a housing of a device with a metallic cord grip or kellumthat secures itself upon the conductive polymeric layer and directlycontacts the housing. Still a further alternative drain could be enabledin the absence of the preferred drain wire through applying a conductiveheat shrink for direct connection between two conductive polymericlayers or to secure a separate connection point for draining EMI. Suchalternatives, however, are believed to be inferior at present to thepreferred embodiment of the drain wire insofar as extended wear or tearin the conductive polymeric layer 30 could cause gaps or breaks in thatlayer which are believed to cause unacceptable degradation in the EMIshielding in the absence of the preferred drain wire (in contrast to thealternative drains falling within the scope of the present invention).

The present invention can be used in a cord reel assembly 100 as shownin FIG. 2. The cord reel assembly of this example includes a housing110, a cover 120, and a spool 130. The spool 130 can be controllablywound or unwound through the use of (for example) a ratchet 122, whichalong with a spring retainer 124 operates to control the mechanics ofwinding and unwinding the cord reel. In this embodiment, the cable 10 isa round cable which terminates at one end inside the inner connectionchamber 140 located inside of the spool 130 in order to connect to afurther cable or electrical connection (such as a flat cable 160). Theinner connection chamber 140 of this example embodiment is detailedfurther in FIG. 3, which includes a splice 142 for connecting the cableand the flat cable 160, a drain mechanism 144, which can be a connectionfrom an exposed end of the drain wire 20 to a ground lug 146, oralternatively can comprise one of the alternate drains detailed above.

The above description is not intended to limit the meaning of the wordsused in the following claims that define the invention. Rather, it iscontemplated that future modifications in structure, function or resultwill exist that are not substantial changes and that all suchinsubstantial changes in what is claimed are intended to be covered bythe claims. For instance, the specific wire gages used in the examplesof the preferred embodiments of present invention is for illustrativepurposes with reference to the example drawings only. Similarly, whilethe preferred embodiments of the present invention are focused upon usewithin a cord reel assembly, those of skill in the art will understandthat the invention has equal applicability to multi-conductor cableswhich cannot be completely encapsulated but still required EMI and crosstalk resistance. Likewise, it will be appreciated by those skilled inthe art that various changes, additions, omissions, and modificationscan be made to the illustrated embodiments without departing from thespirit of the present invention. All such modifications and changes areintended to be covered by the following claims.

We claim:
 1. A cord reel assembly comprising: a) a housing, b) a spoollocated within the housing; and c) at least one cable for winding andunwinding around the spool, the cable having a substantially roundcross-sectional profile comprising: i) at least one power conductor; ii)at least one drain wire; iii) a conductive polymeric layer surroundingthe at least one power conductor, wherein the conductive polymeric layercontacts and surrounds at least a portion of the at least one drainwire, and at least one end of the at least one drain wire is not coveredby the conductive polymeric layer and contacts at least one of thehousing or the spool.
 2. The cord reel assembly of claim 1, wherein theconductive polymeric layer is ETFE.
 3. The cord reel assembly of claim1, wherein the drain wire is comprised of tinsel.
 4. A cord reelassembly comprising: a) a housing, b) a spool located within thehousing; and c) at least one cable for winding and unwinding around thespool, the cable having a substantially round cross-sectional profilecomprising: i) at least one data conductor; ii) at least one drain wire;iii) a conductive polymeric layer surrounding the at least one dataconductor, and wherein the conductive polymeric layer contacts andsurrounds at least a portion of the at least one drain wire, and atleast one end of the at least one drain wire is not covered by theconductive polymeric layer and contacts at least one of the housing orthe spool.
 5. The cord reel assembly of claim 1, wherein the conductivepolymeric layer is ETFE.
 6. A cord reel assembly comprising: a) ahousing, b) a spool located within the housing; and c) at least onecable for winding and unwinding around the spool, the cable having asubstantially round cross-sectional profile comprising: i) at least onedata conductor; ii) at least one power conductor; iii) at least onedrain wire; iv) a conductive polymeric layer surrounding the at leastone data conductor, and the at least one power conductor, wherein theconductive polymeric layer contacts the at least one drain wire.
 7. Thecord reel assembly of claim 18, wherein the at least one end of the atleast one drain wire is not covered by the conductive polymeric layer.8. A cord reel assembly comprising: a) a housing, b) a spool locatedwithin the housing; and c) at least one cable for winding and unwindingaround the spool, the cable having a substantially round cross-sectionalprofile comprising: i) at least one data conductor; ii) at least onepower conductor; iii) at least one drain; iv) a conductive polymericlayer surrounding the at least one data conductor, and the at least onepower conductor, wherein the conductive polymeric layer contacts the atleast one drain.
 9. The cord reel assembly of claim 8, wherein theconductive polymeric layer is ETFE.
 10. A cord reel assembly comprising:a) a housing, b) a spool located within the housing; and c) at least onecable for winding and unwinding around the spool, the cable having asubstantially round cross-sectional profile comprising: i) at least onedrain wire; ii) at least one conductor; iii) a conductive polymericlayer surrounding the at least one conductor, wherein the conductivepolymeric layer contacts the at least one drain wire and conducts to atleast one of the housing or the spool.
 11. A cord reel assemblycomprising: a) a housing, b) a spool located within the housing; and c)at least one cable for winding and unwinding around the spool, the cablehaving a substantially round cross-sectional profile comprising: i) atleast one drain mechanism; ii) at least one conductor; iii) a conductivepolymeric layer surrounding the at least one conductor, wherein theconductive polymeric layer contacts the at least one drain mechanism.12. A cord reel assembly comprising: a) a housing, b) a spool locatedwithin the housing; and c) at least one cable for winding and unwindingaround the spool, the cable having a substantially round cross-sectionalprofile comprising: (i) at least one data conductor; (ii) at least onepower conductor; (iii) at least one drain wire; (iv) a conductivepolymeric layer surrounding the at least one data conductor, and the atleast one power conductor, wherein the conductive polymeric layercontacts the at least one drain wire.